It’s hard to imagine the new comedies from Michael J. Fox and Robin Williams being very good. Many years have passed since they were sitcom stars, and the nature of TV humor has changed; it has gotten less schmaltzy and more coolly ironic. Fox left “Spin City” in 2000 to spend time with his family and promote Parkinson’s research, and Williams’s “Mork and Mindy” was canceled in 1982. Since then, TV has undergone a single-camera revolution, and the cringe-toned likes of “The Office” and “30 Rock” have come and gone.

It’s also hard to imagine the new sitcoms from Fox and Williams, which premiere opposite each other Thursday at 9 p.m., being deeply awful — especially Fox’s. Since Fox left his series, he has put in a few unforgettable guest stints on “The Good Wife,” “Rescue Me,” and “Curb Your Enthusiasm,” each time proving that he’s still in fine form despite his disease, that his timing is still spot on. And Williams, a movie star, would only return to TV if the material were good enough, right?

Well, the shows are neither awful nor awesome, so there’s no easy answer. Both begin their runs as boilerplate comedies that could either improve, given the right kind of nurturing, or quickly become unbearable.

Williams’s “The Crazy Ones” on CBS is the one with the greater potential, and not so much because of Williams and his shtick — the different voices, the fast talking, the gay affect, the manic whatever. The weakest moments in the premiere are when Williams seems to be improvising on the script, automatically doing his Williams thing as if a switch had been thrown on. The potential comes mostly from the supporting cast, namely James Wolk (Bob Benson on “Mad Men”) and Hamish Linklater, who was Julia Louis-Dreyfus’s brother on “The New Adventures of Old Christine.” By the end of the half-hour, I was ready to watch a show with just the two of them — and with special guest star Kelly Clarkson, who nearly steals the show.

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Created by David E. Kelley of “Ally McBeal” and “Boston Legal,” “The Crazy Ones” borrows a bit from “Mad Men,” since it’s set in a struggling Chicago ad agency. Williams is the owner, Sarah Michelle Gellar — as stiff as ever — is his cool, responsible daughter. In the premiere, they work to hold onto the McDonald’s account by trying to coax Clarkson into singing a McDonald’s jingle. The product tie-in is tiresome, but Wolk in particular, with his winks and grins, adds warmth as Williams’s cocky protege. He also rescues a few scenes in which Williams starts to drift into the nonsense stratosphere.

THE MICHAEL J. FOX SHOW

Cast:

Michael J. Fox, Betsy Brandt, Wendell Pierce, Katie Finneran

Network:

NBC

Show date:

Thursday

Show time:

9-9:30 and 9:30-10 p.m.

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NBC’s “The Michael J. Fox Show,” which opens with a pair of episodes, won’t have different clients and ad campaigns to add color each week. It’s essentially a traditional family sitcom with a very present New York setting. Fox plays a version of himself named Mike Henry, who returns to the news anchor job he left years earlier because of his Parkinson’s. Meta meanings run amok, as the Parkinson’s jokes fill the air and as Mike hates the way the public treats him like a hero. In episode two, Fox’s real life wife, Tracy Pollan, guest stars as a flirtatious neighbor.

Richard Cartwright/CBS

Robin Williams, Sarah Michelle Gellar in “The Crazy Ones.”

Essentially, the story is Mike’s wife, played by Betsy Brandt of “Breaking Bad,” dealing with his neuroses while their three kids roll their eyes like all sitcom kids. In that second episode, each kid walks into their parents’ room without knocking while their parents are trying to make love — yes, it’s filled with that kind of overfamiliar farce. It’s nice to see Fox in primetime again, and he isn’t the problem with the show. The problem is the writing, which is domestic comedy at its laziest. You’ve seen this material before, and before that, too.